| Ticketrhythm Limited | Information & communication | 2015 |
| Tiger Optics Media Ltd | Information & communication | 2015 |
| Tigris Consulting Services (UK) Limited | Administrative & support | 2014 |
| TIM Alden Tree Surgery Limited | Agriculture & fishing | 1999 |
| Timber Restoration Company Limited | Construction | 2004 |
| Titan Social Ltd | Arts & recreation | 2024 |
| TJ Foodtech Ltd | Manufacturing | 2026 |
| TJB Business Advisory Services Limited | Professional & scientific | 2010 |
| TJK Automotive Limited | Wholesale & retail | 2012 |
| TJK Outdoor Living Ltd | Construction | 2018 |
| TL Consult Limited | Professional & scientific | 2015 |
| TLS Management Services Limited | Financial services | 2006 |
| TM2 Design Ltd | Construction | 2013 |
| TML Care Solutions Limited | Health & social care | 2011 |
| TMP Scaffolding Limited | Construction | 2018 |
| TNR Construction & Plant Hire Ltd | Construction | 2024 |
| TO Harrington Ltd | Administrative & support | 2022 |
| TO LA Brand Ltd | Wholesale & retail | 2023 |
| Toby James Construction Limited | Arts & recreation | 2021 |
| TOM VH Creative Limited | Arts & recreation | 2024 |
| TOO Mortgage Services Ltd | Extraterritorial | 2023 |
| Top J Ltd | Wholesale & retail | 2024 |
| Topcnc Ltd | Professional & scientific | 2019 |
| Topcourses Leicester Ltd | Education | 2021 |
| Topwok MH Limited | Hospitality | 2025 |
| Toral Davda Ltd | Information & communication | 2014 |
| Toro Installations Limited | Administrative & support | 2014 |
| Torwalk Limited | Real estate | 2001 |
| Towrite Electric Vehicles (Harborough) Limited | Manufacturing | 1989 |
| Toynamics UK and Ireland Limited | Wholesale & retail | 2002 |
| TP Interiors Ltd | Construction | 2025 |
| TR Golf Ltd | Administrative & support | 2009 |
| Tracksyuk Ltd | Wholesale & retail | 2026 |
| Tradesure Commercials Ltd | Wholesale & retail | 2025 |
| Traditional Outbuildings Limited | Construction | 2026 |
| Traintalk Limited | Other services | 2013 |
| Transit Retail Services Limited | Administrative & support | 1994 |
| Transula Limited | Administrative & support | 2017 |
| Traynor & Sons Home Improvements Ltd | Construction | 2017 |
| TRC Windows Ltd | Manufacturing | 2019 |
| Trenchcrete Limited | Manufacturing | 2019 |
| Trend Diabetes Ltd | Health & social care | 2019 |
| Trend Horses Ltd | Arts & recreation | 2025 |
| Trevelyan Accessories Limited | Wholesale & retail | 2009 |
| Triac Air Conditioning Limited | Construction | 1992 |
| Triple Skillz in the Community Limited | Education | 2017 |
| Tripleglow Limited | Real estate | 1982 |
| Triplegrid NO1 Limited | Construction | 2017 |
| Triplicar Holdings Limited | Hospitality | 2023 |
| Troubador Publishing Limited | Information & communication | 1996 |
| True North Capital Investment Limited | Real estate | 2017 |
| True North Capital Limited | Real estate | 2016 |
| Trust Inclusion Limited | Professional & scientific | 2023 |
| Tsrl Limited | Professional & scientific | 2003 |
| TT INT Ltd | Wholesale & retail | 2025 |
| TT Projects Ltd | Administrative & support | 2016 |
| Tubbsmobilecatering Limited | Hospitality | 2022 |
| Tubby's Cafes Limited | Real estate | 1945 |
| Tughan Pharma Consultants Ltd | Professional & scientific | 2020 |
| Turnkey Filtration Limited | Professional & scientific | 2025 |
| Tvprofessionals Limited | Information & communication | 2009 |
| Twer Limited | Administrative & support | 2017 |
| Twin Finance Limited | Financial services | 2015 |
| Two Old Goats Ltd | Hospitality | 2023 |
| Two Quarts Arts Community Interest Company | Arts & recreation | 2026 |
| Two Two Enterprises Limited | Information & communication | 2015 |
| Twynham Components Ltd | Wholesale & retail | 2004 |
| Tykes Investments Ltd | Professional & scientific | 2007 |
| Tyning Village Limited | Construction | 2005 |
| Tyraxer Ltd | Administrative & support | 2024 |
| Tyre Wall Stickers Limited | Manufacturing | 2015 |
| UK Finclusion | Education | 2019 |
| Ukiwi Ltd | Administrative & support | 2017 |
| Ukwa Limited | Other services | 2010 |
| Ultimate Coldplay Ltd | Arts & recreation | 2019 |
| Ummah Energy Ltd | Administrative & support | 2024 |
| Underdark Collective Limited | Professional & scientific | 2022 |
| Underwood Kitchens and Interiors Ltd | Manufacturing | 2025 |
| Unique Beauty Therapy Limited | Other services | 2011 |
| Unique Optical Solutions Ltd | Health & social care | 2011 |
| Unlimited Coworking Limited | Real estate | 2023 |
| Unlimited Potential Group Ltd | Professional & scientific | 2025 |
| Unphiltered Ltd | Professional & scientific | 2025 |
| Unyte Academy Ltd | Education | 2022 |
| Unyte BIO Char Ltd | Manufacturing | 2024 |
| Unyte Bioconstruct Ltd | Manufacturing | 2021 |
| Unyte Capital Ltd | Financial services | 2018 |
| Unyte Energy Ltd | Energy | 2019 |
| Unyte Health Ltd | Wholesale & retail | 2017 |
| Unyte Hemp Ltd | Manufacturing | 2018 |
| Unyte Holdings Ltd | Agriculture & fishing | 2025 |
| Unyte Invest Ltd | Financial services | 2018 |
| Unyte Medical Limited | Manufacturing | 2018 |
| Unyte Retrofit Ltd | Construction | 2021 |
| Unyte Waste Limited | Water & waste | 2011 |
| Upper Limb Consulting LLP | | 2016 |
| Upper Limb Ltd | Health & social care | 2010 |
| Upper London Limited | Professional & scientific | 2014 |
| Uppingham Gutter Services Ltd | Administrative & support | 2024 |
| Uppingham Slabbing Services Ltd | Administrative & support | 2024 |